1. Field of the Invention
The present invention relates to an accelerator control system for an automotive vehicle and more specifically to an accelerator control system in which appropriate accelerator control characteristics are automatically selected according to vehicle travelling conditions or accelerator pedal depression conditions.
2. Description of the Prior Art
In automotive vehicles, an accelerator pedal is mechanically connected or linked directly to a throttle valve through a wire or a link mechanism, so that the opening rate of the throttle valve can be directly adjusted as the accelerator pedal is depressed by the driver.
However, in the prior-art mechanical accelerator device, the accelerator control characteristics representative of the relationship between throttle valve opening rate and accelerator pedal stroke are fixedly determined in dependence upon the mechanical structure of the accelerator device such as the throttle valve actuating device. In other words, these accelerator pedal control characteristics between accelerator pedal stroke and throttle valve opening rate are fixedly, unselectably or unadjustably predetermined according to the types of throttle devices.
Therefore, some types of throttle devices are provided with characteristics such that throttle valve opening rate increases relatively sharply with increasing accelerator pedal stroke. These control characteristics are appropriate when a vehicle is travelling at a relatively high speed on a highway but not appropriate when the vehicle is travelling at a relatively low speed on a busy street. In more detail, when a vehicle is travelling at a high speed on a highway, these control characteristics are suitable because the driver sometimes needs to quickly accelerate the vehicle in order to avert an accident. However, when the vehicle is travelling at a low speed on a busy street, these control characteristics are not suitable because the driver often needs to repeatedly drive the vehicle only a short distance forward and it is rather difficult for the driver to repeatedly depress the accelerator pedal finely and skillfully.
In contrast with this, some other types of throttle devices are provided with characteristics such that throttle valve opening rate increases relatively gently with increasing accelerator pedal stroke. These control characteristics are appropriate when a vehicle is travelling at a relatively low speed on a busy street but not appropriate when the vehicle is travelling at a relatively high speed on a highway. This is because the driver must depress the accelerator pedal deeply or excessively when accelerating the vehicle quickly on a highway to avert an accident.
In summary, in the prior-art throttle devices for automotive-vehicles, there exists a problem in that it is impossible to obtain appropriate accelerator control characteristics representative of the relationship between throttle valve opening rate and accelerator pedal stroke according to vehicle travelling conditions.